Looking for a 3.5inch to 4inch adaptor/reducer

Hi, I'm looking to replace an old 3.5inch cast iron soil pipe with new uPVC 4inch soil pipe, but I cannot find an adaptor to suit? I looked at the McAlpine coupling with the rubber fins, but don't know if that would fit into the smaller cast iron pipe? I intend to replace the pipe from the ground up.... anyone know if the McAlpine adaptor can be used or if there is a better option or better way to do it?

Thanks

 

[ShaunCorbs]

mcalpine dc1 should fit or a time saver coulping